[clang] [ObjC] Check entire chain of superclasses to see if class layout can be statically known (PR #81335)
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Wed Feb 21 09:13:38 PST 2024
https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/81335
>From 147e27730c9ce5f7baef7363480e98b08190f476 Mon Sep 17 00:00:00 2001
From: Rose <83477269+AtariDreams at users.noreply.github.com>
Date: Fri, 9 Feb 2024 17:51:15 -0500
Subject: [PATCH 1/2] [ObjC] Add pre-commit tests [NFC]
---
.../constant-non-fragile-ivar-offset.m | 70 +++++++++++++++++++
1 file changed, 70 insertions(+)
diff --git a/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m b/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
index 788b3220af3067..0bf3336527b0a0 100644
--- a/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
+++ b/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
@@ -1,6 +1,12 @@
// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -emit-llvm %s -o - | FileCheck %s
// CHECK: @"OBJC_IVAR_$_StaticLayout.static_layout_ivar" = hidden constant i64 20
+// CHECK: @"OBJC_IVAR_$_SuperClass.superClassIvar" = hidden constant i64 20
+// CHECK: @"OBJC_IVAR_$_SuperClass._superClassProperty" = hidden constant i64 24
+// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar" = global i64 32
+// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar2" = global i64 40
+// CHECK: @"OBJC_IVAR_$_IntermediateClass._intermediateProperty" = hidden global i64 48
+// CHECK: @"OBJC_IVAR_$_SubClass.subClassIvar" = global i64 56
// CHECK: @"OBJC_IVAR_$_NotStaticLayout.not_static_layout_ivar" = hidden global i64 12
@interface NSObject {
@@ -20,6 +26,70 @@ -(void)meth {
}
@end
+// Ivars declared in the @interface
+ at interface SuperClass : NSObject
+ at property (nonatomic, assign) int superClassProperty;
+ at end
+
+ at implementation SuperClass {
+ int superClassIvar; // Declare an ivar
+}
+- (void)superClassMethod {
+ _superClassProperty = 42;
+ superClassIvar = 10;
+ // CHECK: load i64, ptr @"OBJC_IVAR_$_SuperClass
+ // CHECK: getelementptr inbounds i8, ptr %1, i64 20
+}
+ at end
+
+// Inheritance and Ivars
+ at interface IntermediateClass : SuperClass
+{
+ double intermediateClassIvar;
+
+ @protected
+ int intermediateClassIvar2;
+}
+ at property (nonatomic, strong) SuperClass *intermediateProperty;
+ at end
+
+ at implementation IntermediateClass
+ at synthesize intermediateProperty = _intermediateProperty;
+- (void)intermediateClassMethod {
+ intermediateClassIvar = 3.14;
+ // CHECK: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
+ // CHECK: getelementptr inbounds i8, ptr %0, i64 %ivar
+}
+
+- (void)intermediateClassPropertyMethod {
+ self.intermediateProperty = 0;
+ // CHECK: getelementptr inbounds i8, ptr %2, i64 24
+}
+ at end
+
+ at interface SubClass : IntermediateClass
+{
+ double subClassIvar;
+}
+ at end
+
+ at implementation SubClass
+- (void)subclassVar {
+
+ subClassIvar = 6.28;
+ // CHECK: load i64, ptr @"OBJC_IVAR_$_SubClass
+ // CHECK: getelementptr inbounds i8, ptr %0, i64 %ivar
+}
+
+-(void)intermediateSubclassVar
+{
+ intermediateClassIvar = 3.14;
+ // CHECK: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
+ // CHECK: getelementptr inbounds i8, ptr %0, i64 %ivar
+}
+
+ at end
+
@interface NotNSObject {
int these, might, change;
}
>From bbaaba0c9cab9a2f09e8c0840fdcedaa1fd2bd2c Mon Sep 17 00:00:00 2001
From: Rose <83477269+AtariDreams at users.noreply.github.com>
Date: Tue, 13 Feb 2024 14:52:49 -0500
Subject: [PATCH 2/2] [ObjC] Check entire chain of superclasses to see if class
layout can be statically known
As of now, we only check if a class directly inherits from NSObject to determine if said class has fixed offsets and can therefore have its memory layout statically known.
However, if an NSObject subclass has fixed offsets, then so must the subclasses of that subclass, so this allows us to optimize instances of subclasses of subclasses that inherit from NSObject and so on.
To determine this, we need to find that the compiler can see the implementation of each intermediate class, as that means it is statically linked.
---
clang/lib/CodeGen/CGObjCMac.cpp | 23 +++++++++++++-----
.../constant-non-fragile-ivar-offset.m | 24 +++++++++----------
2 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 27d77e9a8a5511..c7ec2370f56285 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -1593,12 +1593,23 @@ class CGObjCNonFragileABIMac : public CGObjCCommonMac {
}
bool isClassLayoutKnownStatically(const ObjCInterfaceDecl *ID) {
- // NSObject is a fixed size. If we can see the @implementation of a class
- // which inherits from NSObject then we know that all it's offsets also must
- // be fixed. FIXME: Can we do this if see a chain of super classes with
- // implementations leading to NSObject?
- return ID->getImplementation() && ID->getSuperClass() &&
- ID->getSuperClass()->getName() == "NSObject";
+ // Test a class by checking its superclasses up to
+ // its base class if it has one.
+ while (ID) {
+ // The layout of base class NSObject
+ // is guaranteed to be statically known
+ if (ID->getName() == "NSObject")
+ return true;
+
+ // If we cannot see the @implementation of a class,
+ // we cannot statically know the class layout.
+ if (!ID->getImplementation())
+ return false;
+
+ // Test superclass
+ ID = ID->getSuperClass();
+ }
+ return false;
}
public:
diff --git a/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m b/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
index 0bf3336527b0a0..7ecb8d1b0d566a 100644
--- a/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
+++ b/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
@@ -3,10 +3,10 @@
// CHECK: @"OBJC_IVAR_$_StaticLayout.static_layout_ivar" = hidden constant i64 20
// CHECK: @"OBJC_IVAR_$_SuperClass.superClassIvar" = hidden constant i64 20
// CHECK: @"OBJC_IVAR_$_SuperClass._superClassProperty" = hidden constant i64 24
-// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar" = global i64 32
-// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar2" = global i64 40
-// CHECK: @"OBJC_IVAR_$_IntermediateClass._intermediateProperty" = hidden global i64 48
-// CHECK: @"OBJC_IVAR_$_SubClass.subClassIvar" = global i64 56
+// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar" = constant i64 32
+// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar2" = constant i64 40
+// CHECK: @"OBJC_IVAR_$_IntermediateClass._intermediateProperty" = hidden constant i64 48
+// CHECK: @"OBJC_IVAR_$_SubClass.subClassIvar" = constant i64 56
// CHECK: @"OBJC_IVAR_$_NotStaticLayout.not_static_layout_ivar" = hidden global i64 12
@interface NSObject {
@@ -23,6 +23,7 @@ @implementation StaticLayout {
-(void)meth {
static_layout_ivar = 0;
// CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_StaticLayout
+ // CHECK: getelementptr inbounds i8, ptr %0, i64 20
}
@end
@@ -37,7 +38,7 @@ @implementation SuperClass {
- (void)superClassMethod {
_superClassProperty = 42;
superClassIvar = 10;
- // CHECK: load i64, ptr @"OBJC_IVAR_$_SuperClass
+ // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_SuperClass
// CHECK: getelementptr inbounds i8, ptr %1, i64 20
}
@end
@@ -57,13 +58,12 @@ @implementation IntermediateClass
@synthesize intermediateProperty = _intermediateProperty;
- (void)intermediateClassMethod {
intermediateClassIvar = 3.14;
- // CHECK: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
- // CHECK: getelementptr inbounds i8, ptr %0, i64 %ivar
+ // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
+ // CHECK: getelementptr inbounds i8, ptr %0, i64 32
}
- (void)intermediateClassPropertyMethod {
self.intermediateProperty = 0;
- // CHECK: getelementptr inbounds i8, ptr %2, i64 24
}
@end
@@ -77,15 +77,15 @@ @implementation SubClass
- (void)subclassVar {
subClassIvar = 6.28;
- // CHECK: load i64, ptr @"OBJC_IVAR_$_SubClass
- // CHECK: getelementptr inbounds i8, ptr %0, i64 %ivar
+ // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_SubClass
+ // CHECK: getelementptr inbounds i8, ptr %0, i64 56
}
-(void)intermediateSubclassVar
{
intermediateClassIvar = 3.14;
- // CHECK: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
- // CHECK: getelementptr inbounds i8, ptr %0, i64 %ivar
+ // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
+ // CHECK: getelementptr inbounds i8, ptr %0, i64 32
}
@end
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